Background: An impediment to the rational development of novel drugs against tuberculosis (TB) is a general paucity of knowledge concerning the metabolism of Mycobacterium tuberculosis, particularly during infection. Constraint-based modeling provides a novel approach to investigating microbial metabolism but has not yet been applied to genome-scale modeling of M. tuberculosis.

An experimental system of Mycobacterium tuberculosis growth in a carbon-limited chemostat has been established by the use of Mycobacterium bovis BCG as a model organism. For this model, carbon-limited chemostats with low concentrations of glycerol were used to simulate possible growth rates during different stages of tuberculosis. A doubling time of 23 h (D ‫؍‬ 0.03 h ؊1 ) was adopted to represent cells during the acute phase of infection, whereas a lower dilution rate equivalent to a doubling time of 69 h (D ‫؍‬ 0.01 h ؊1 ) was used to model mycobacterial persistence. This chemostat model allowed the specific response of the mycobacterial cell to carbon limitation at different growth rates to be elucidated. The macromolecular (RNA, DNA, carbohydrate, and lipid) and elemental (C, H, and N) compositions of the biomass were determined for steady-state cultures, revealing that carbohydrates and lipids comprised more than half of the dry mass of the BCG cell, with only a quarter of the dry weight consisting of protein and RNA. Consistent with studies of other bacteria, the specific growth rate impacts on the macromolecular content of BCG and the proportions of lipid, RNA, and protein increased significantly with the growth rate. The correlation of RNA content with the growth rate indicates that ribosome production in carbon-limited M. bovis BCG cells is subject to growth rate-dependent control. The results also clearly show that the proportion of lipids in the mycobacterial cell is very sensitive to changes in the growth rate, probably reflecting changes in the amounts of storage lipids. Finally, this study demonstrates the utility of the chemostat model of mycobacterial growth for functional genomic, physiology, and systems biology studies.With three million people dying from tuberculosis (TB) annually, Mycobacterium tuberculosis remains a formidable pathogen. Tuberculosis ranks among the top 10 causes of global mortality and morbidity and is the leading cause of infectious disease (66). The ability of M. tuberculosis to adapt to and survive harsh environmental conditions in order to establish and maintain long-term infections within its human host is fundamental to this organism's success. Modification of the mycobacterial cell in response to changes in the environment is crucial to this adaptive process, but detailed information about how M. tuberculosis changes its macromolecular composition in response to its environment and growth rate is lacking.The genome sequence of M. tuberculosis has been available since 1998 (9). Although information obtained from the genome sequence provided new and valuable insights into the biology of the tubercle bacillus, the genome itself provides few clues regarding how the pathogen responds to its environment by changing its cellular composition. One of the principal tasks of postgenomic biological studies of M. tuberculosis is to understand how the genome orchestrates the structure and dynamics of the cell in response to changes in the environment. This task requires an integrat...

The cellulosic part of rice straw was modified to develop N-halamine 11 derivatives for disinfection. The process involved cross-linking of the cellulosic material 12 with amino/amide/imide containing compounds; cyclic and acyclic. The structures of the 13 prepared materials were identified using FTIR and solid state 13 CNMR. The modified 14 materials were halogenated to form N-halamines and the antimicrobial activity of each 15 evaluated against examples of Gram-positive (Staphylococcus aureus) and Gram-16 negative bacteria (Escherichia coli) using a variety of methods; agar plate, blended agar, 17 stirred flask and in columns. One of the N-halamines achieved a 9 log reduction against 18 both E. coli and S. aureus in 4 hours. In addition, no S. aureus growth was recorded on 19 agar plates blended with 0.5g of this same material. 20

The adaptation of the tubercle bacillus to the host environment is likely to involve a complex set of gene regulatory events and physiological switches in response to environmental signals. In order to deconstruct the physiological state of Mycobacterium tuberculosis in vivo, we used a chemostat model to study a single aspect of the organism's in vivo state, slow growth. Mycobacterium bovis BCG was cultivated at high and low growth rates in a carbon-limited chemostat, and transcriptomic analysis was performed to identify the gene regulation events associated with slow growth. The results demonstrated that slow growth was associated with the induction of expression of several genes of the dormancy survival regulon. There was also a striking overlap between the transcriptomic profile of BCG in the chemostat model and the response of M. tuberculosis to growth in the macrophage, implying that a significant component of the response of the pathogen to the macrophage environment is the response to slow growth in carbon-limited conditions. This demonstrated the importance of adaptation to a low growth rate to the virulence strategy of M. tuberculosis and also the value of the chemostat model for deconstructing components of the in vivo state of this important pathogen.Despite more than a century of research into tuberculosis (TB), this disease remains the number one killer due to a single infectious agent, making Mycobacterium tuberculosis one of the most successful human pathogens. A key to this bacterium's success is its ability to establish and maintain a latent infection in its human host for many decades (18). The control of TB is severely impeded by the global magnitude of latent TB. Onethird of the world's population is estimated to harbor persistent M. tuberculosis primed for reactivation and initiation of clinical disease (7). The bacterial response to the triggers of latency and reactivation are very poorly understood. Determining the mechanisms involved during the establishment, maintenance, and reactivation of latent TB is an important goal for mycobacterial researchers. Such information should lead to the development of novel therapeutics, vaccines, and diagnostic strategies targeted to persistent M. tuberculosis.In vitro modeling of M. tuberculosis provides simple experimental approaches for studying the physiology and genetic basis of TB. However, the design of adequate models is impeded by the paucity of knowledge about the biological characteristics of both the bacteria and the host environment during human TB, and therefore in vitro modelers must make simplistic assumptions about the environmental variables within the human host. Microaerophilic adaptation, nutrient starvation, drug-persistent, and extended stationary-phase models of persistent TB have been established (9). All these models provide in vitro conditions that are intended to simulate the microenvironments of the host during persistence. While these models have proved to be very valuable for studying persistence, it is unlikely that a sin...

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An N-Halamine biocidal polymer was prepared by co-polymerizing toluene-2,6-diisocyanate with a new heterocyclic uramil-based azo-monomer, followed by halogenation. The mode of action of N-halamine polymers on bacteria was investigated and halogenation conditions (temperature, halogenation time, halogen concentration) were optimized for bactericidal action against E. coli and S. aureus. It was found that the mode of action of this type of polymer is a combination of different factors; contact, release, and through interaction of the polymer with the bacterial medium. The most effective halogenation conditions were stirring 1 g polymer in 10 mL sodium hypochlorite (10 %) for 1 h at ambient temperature (22 C).

A miniature electrode was used to measure, for the first time, the timedependent change in dissolved oxygen concentration of small-scale cultures of two actinomycete species at various aeration efficiencies in both complex and defined media. Erythromycin was produced in both oxygen-limited and oxygen-sufficient conditions in shaken flask and inclined tube cultures of Saccharopolyspora erythraea and a further, novel, secondary metabolite was produced only under oxygen limitation. In contrast, vancomycin was only produced in oxygen-suff icient cultures of Amycolatopsis orientalis. Similar results were obtained in batch bioreactor cultures. These findings indicate that oxygen limitation acts in an analogous manner to substrate limitation imposed by dissolved nutrients, stimulating secondary metabolite production in some cases and inhibiting it in others. The implications of these findings in screening programmes for novel secondary metabolites are discussed.